Lightcurve Analysis and Photometry on CCD Images of Asteroids ...

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First <strong>and</strong> Second Order Extinctions The value for extinction is not the same for all colors. Red light is absorbed less by the earth’s atmosphere than blue light, the value for extinction is lower for red light than blue. First order is the type of extinction just described, i.e., the value for a fixed or narrow range of colors. Second order extinction is dependent on the color of the object being measured. (Mostly critical for stellar photometry – variable star observations) As the object moves towards the horizon from its highest point in the sky, the blue portion of its light is dimmed more rapidly than the red portion. Therefore, to correctly compute the true "exospheric magnitude" of the star (magnitude as seen outside the earth’s atmosphere), one must also determine the second order extinction.
PhotoRed: Transforms & Extinctions M f = (m - k’ f X - k” f XCI) + T f CI + ZP f M f is the reduced magnitude on st<strong>and</strong>ard system m is instrumental magnitude k’ f is first order extinction for filter (f) X is air mass k” f is the second order extinction for filter (f) T f is the transform for filter (f) CI is color index ZP f is the nightly zero point for filter (f)
Page 1 and 2: NASA Meteoroid Environment Office M
Page 3 and 4: Why Study Rocks in Space? NASA’s
Page 5 and 6: Photometry Primer
Page 7 and 8: Astronomy by Ground-Based Observato
Page 9 and 10: PhotoRed: Transforms & Extinctions
Page 11: First and Second O
Page 15 and 16: PhotoRed Transforms / Extinction Pl
Page 17 and 18: Comet CK75
Page 19: SPECIAL THANKS: NASA Marshall SFC N

Lightcurve Analysis and Photometry on CCD Images of Asteroids ...

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